Happy Christmas or Merry Christmas?

As strange as it sounds, i don't associate the 'Christ' part with Christmas at all, it's just the name of the bit of the season when Santa shows up and the presents are handed out and i have never been wished, or been wished, Happy Holidays, that makes me think of someone going off on their summer holidays, and the only time i have seen 'Season's Greetings' is on a Christmas Card so i go for either Happy Christmas or Merry Christmas.  
I don't give a second thought to whether a person celebrates it or not, i wish them a Happy/Merry Christmas anyway and leave it up to them to either accept it or ignore it as they wish but i did ask a lexicographer a while ago which is correct, Merry or Happy Christmas?
Apparently, the old saying of 'Merry Christmas' dates back to the Middle Ages and means to enjoy the alcohol, food and general revelry which comes with Christmas while 'Happy Christmas' means enjoy the decorations, twinkling lights and genial atmosphere which comes with the season.
Makes sense i guess as 'Happy' is a word that describes an emotional condition, the state of 'being happy' while 'Merry' is more of a behavior descriptor as in the act of merry-making.
Something i have never noticed until it was pointed out is that when the Queen does her thing on Christmas Day, she always wishes all her subjects a 'Happy Christmas' and never a Merry one because of the connotations of 'merry' which is associated with the excess and rowdiness of Christmas.
I guess what it boils down to is if the person you are about to say it to is the sort who will neck a dozen bottles of WKD Blue, eat their own weight in mince pies and fall asleep face down in their Christmas Pudding then it's Merry Christmas otherwise it's safer to go with the Queen and say Happy Christmas.
Either way, regardless of what you say, the sentiment is to have an enjoyable time over the Christmas period and you hope they have a good time however they spend it except when you say it to right-wing politicians, we all hope they have a rotten Christmas.